1. Field of the Invention
The present invention relates to an optical transmission apparatus in which a plurality of nodes are connected to one another via optical couplers.
2. Description of the Related Art
Conventionally, a connection between nodes such as boards (circuit boards) or apparatuses is electrically conducted by a configuration shown in FIG. 1. As shown in FIG. 1, depending on the kind of a signal, nodes #0 to #N are bus-connected to one another via a bus 10, or link connections between node #0 and nodes #1 to #N are conducted in a one-to-one relationship via signal lines 11.
A method in which an optical bus is used in order to bus-connect at a high speed a plurality of nodes to one another is known. For example, JP-B-5-61821 discloses a technique in which nodes are bus-connected by connecting fibers of one-to-one connection in cascade. JP-A-2-41042 discloses a serial optical data bus for loop transmission between circuit boards in which two sets of light emitting/light receiving devices are placed on the front and rear faces of the circuit boards, and the light emitting/light receiving devices of adjacent ones of the circuit board mounted on a system frame are coupled to one another spatially and optically. JP-A-8-166842 and JP-A-10-268147 disclose a bus connection using an optical star coupler.
Among the methods using an optical bus, however, the method in which cascade connection is conducted has a problem in latency, and the other methods have a problem in that an addition of a one-to-one link connection is not considered. When the example of the electrical connection shown in FIG. 1 is to be configured by using an optical system, a method may be employed in which optical fiber couplers are used in the bus connection and one-to-one connections of optical fibers are used in the link connection. However, this method has a problem in that the configuration is complicated depending on the kind or the number of signal lines.